This invention relates to an improved catalytic reforming process. In another aspect, this invention relates to a method for inhibiting the deactivation of a reformer catalyst. In a further aspect, this invention relates to a method for reactivating a partially deactivated reformer catalyst.
Catalytic reforming is a well established refining process employed by the petroleum industry for upgrading low-octane hydrocarbons to higher-octane hydrocarbons. Typically, catalytic reforming involves the contacting of a naphtha hydrocarbon feed with a reformer catalyst under elevated temperatures and pressures.
Reformer catalysts typically comprise a metal hydrogen transfer component or components, a halogen component, and a porous inorganic oxide support. A reformer catalyst which has been employed widely throughout the petroleum industry comprises platinum as the metal hydrogen transfer component, chlorine as the halogen component, and alumina as the support. Also, additional metallic promoter components, such as rhenium, iridium, ruthenium, tin, palladium, germanium and the like, have been added to the basic platinum-chlorine-alumina catalyst to create a bimetallic catalyst with improved activity, selectivity, or both.
In a conventional reforming process, a series of two to five reformer reactors constitute the heart of the reforming unit. Each reformer reactor is generally provided with a fixed bed or beds of catalyst which receive upflow or downflow feed. Each reactor is provided with a heater because the reactions which take place therein are predominantly endothermic. In a typical commercial reformer, a naphtha feed with a diluent of hydrogen or hydrogen recycled gas is passed through a preheat furnace, then downward through a reformer reactor, and then in sequence through subsequent interstage heaters and reactors connected in series. The product of the last reactor is separated into a liquid fraction and vaporous effluent. The vaporous effluent, a gas rich in hydrogen, may then be used as hydrogen recycled gas in the reforming process.
During operation of a conventional catalytic reforming unit, the activity of the reformer catalyst gradually declines over time. There are believed to be several causes of reformer catalyst deactivation, including, (1) formation of coke within the pores, as well as on the surface, of the catalyst, (2) agglomeration of the catalyst metal component or components, and (3) loss of the halogen component. Deactivation of a reformer catalyst can have the following negative impacts on the reforming process: (1) lower product octane number; (2) higher required reaction temperature; (3) higher required reaction pressure; (4) decreased time between required catalyst regeneration (cycle time); (5) increased requirement for hydrogen; and (6) decreased selectivity.
It has been previously recognized that the deactivation of a reformer catalyst can be inhibited by contacting the reformer catalyst with a chlorine-containing compound during reforming. This xe2x80x9cchloridingxe2x80x9d of the reformer catalyst is thought to inhibit catalyst deactivation by (1) counteracting the formation of coke on the catalyst, (2) redispersing the metal component or components of the catalyst in a more uniform manner, and (3) replacing the halogen component which has been stripped from the catalyst during reforming.
Chloriding of a reformer catalyst is generally achieved by injecting a chlorine-containing additive into the hydrocarbon feed charged to the reformer reactor. The chlorine-containing compound is then carried by the hydrocarbon feed into the reformer reactor where it is contacted with the reformer catalyst in a reaction zone.
Past chloriding methods required that the amount of water present in the reaction zone be controlled during the chloriding of a reformer catalyst. The presence of water in the reaction zone of a reformer reactor is generally undesirable because water can cause accelerated coking of the reformer catalyst as well as stripping of the reformer catalyst""s halogen component; however, past chloriding methods teach that the presence of water in the reformer reaction zone before, during, or after chloriding is necessary to counteract the excessive hydrocracking which is typically encountered when chloriding a reformer catalyst. Thus, prior to the discovery of the invention taught herein, chloriding of a reformer catalyst in a substantially water-free reaction zone without adding water to the reaction zone before, during, or after chloriding was thought to cause catalyst deactivation.
It is an object of the present invention to provide an improved reforming process employing a novel method which inhibits deactivation of a reformer catalyst.
It is a further object of the present invention to provide an improved reforming process employing a novel method which reactivates a partially deactivated reformer catalyst.
Further, objects and advantages of the present invention will become apparent from consideration of the specification and appended claims.
Accordingly, one embodiment of the invention is a reforming process that comprises charging a substantially water-free hydrocarbon feed comprising a reformable hydrocarbon to a reformer reactor operated under reforming conditions. Thereafter, a chlorine-containing additive is introduced, without the simultaneous introduction of water, into the substantially water-free hydrocarbon feed being charged to the reformer reactor operated under reforming conditions in an amount and for a time period that are effective to inhibit deactivation of the reformer catalyst. Thereafter, the introduction of the chlorine-containing additive is terminated and the charging of the substantially water-free hydrocarbon feed to the reformer reactor operated under reforming conditions is continued.
Another embodiment of the invention is a reforming process that comprises charging a substantially water-free hydrocarbon feed comprising a reformable hydrocarbon to a reformer reactor operated under reforming conditions for a time period such that the activity of the reformer catalyst decreases to an unacceptable activity. When the activity of the reformer catalyst has declined to an unacceptable activity, perchloroethylene is introduced, without the simultaneous introduction of water, into the substantially water-free hydrocarbon feed in an amount and for a time period that are effective to restore at least a portion of the decrease in the activity of the reformer catalyst. Thereafter, the introduction of the chlorine-containing additive is terminated and the charging of the substantially water-free hydrocarbon feed to the reformer reactor operated under reforming conditions is continued.
Another embodiment of the invention is a reforming process that comprises contacting, under reforming conditions, a reformer catalyst with a substantially water-free hydrocarbon feed containing a concentration of a chlorine-containing additive for a time period that is effective to inhibit deactivation of the reformer catalyst. Thereafter, contacting, under reforming conditions the reformer catalyst with a substantially water-free hydrocarbon feed which contains substantially no chlorine-containing additive.